Dresden (German pronunciation; Czech: Drážďany, Polish: Drezno) is the capital city and, after Leipzig, the second-largest city of the Free State of Saxony in Germany. It is situated in a valley on the River Elbe, near the border with the Czech Republic. Dresden has a long history as the capital and royal residence for the Electors and Kings of Saxony, who for centuries furnished the city with cultural and artistic splendour. The city was known as the Jewel Box, because of its baroque and rococo city centre. The controversial American and British bombing of Dresden in World War II towards the end of the war killed approximately 25,000 people, many of whom were civilians, and destroyed the entire city centre. After the war restoration work has helped to reconstruct parts of the historic inner city, including the Katholische Hofkirche, the Zwinger and the famous Semper Oper. Since German reunification in 1990 Dresden is again a cultural, educational and political centre of Germany and Europe. The Dresden University of Technology is one of the 10 largest universities in Germany and part of the German Universities Excellence Initiative. The economy of Dresden and its agglomeration is one of the most dynamic in Germany and ranks first in Saxony. It is dominated by high-tech branches, often called as “Silicon Saxony”. The city is also one of the most visited in Germany with 4.3 million overnight stays per year. The royal buildings are among the most impressive buildings in Europe. Main sights are also the nearby National Park of Saxon Switzerland, the Ore Mountains and the countryside around Elbe Valley and Moritzburg Castle. The most prominent building in the city of Dresden is the Frauenkirche. Built in the 18th century, the church was destroyed during World War II. The remaining ruins were left for 50 years as a war memorial. The remains were also left in the city center of Dresden because funds to rebuild the Frauenkirche were scarce. The newly built Frauenkirche has charred stones from the destroyed church adapted with new stones as a reminder of the destruction from World War II. The church was rebuilt from 1994 to 2005.